My good friends took me to the Mercedes-Benz Museum this past June and I was quite impressed. Not only are the cars great and in superb condition, but the design of the building is pretty cool. It overlooks their factory and test track which was in use when I went.
As you walk through the display, it feels like you're walking down a parking garage. Mercedes has their displays in historical order and has historical events inserted in the Mercedes timeline.The museum really is for everybody and not just car buffs. It even has some interactive displays for children. The written display is in English too, so it's really not necessary to get the audio guides.
The admission price is 8 Euros and it is well worth it. They do have a racing simulator for 4 Euros extra but in my opinion that can be skipped.